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OCC Lathrop Site Soil and Groundwater Samplini ork Plan April 28, 2000 percent bentonite powder placed through a tremie pipe and completed with an above-ground well monument. The Waterloo System will be constructed with 7 sampling ports. Groundwater sampling ports will be set at depths corresponding to soil sampling intervals obtained from the soil core. Waterloo System sampling ports will be set at approximately 75 feet bgs, 95 feet bgs, 115 feet bgs, 135 feet bgs, 155 feet bgs, 175 feet bgs, and 195 feet bgs. Actual depth for installation of sampling ports will be determined by the project geologist based on field conditions observed during collection of soil samples. Each groundwater sampling port will be equipped with a dedicated sampling pump to eliminate potential cross contamination between zones. A schematic showing construction details of a typical Waterloo System and geologic conditions encountered in adjacent borehole PW-18 is provided in Figure 2. Product information packages providing additional information regarding the Waterloo System are provided as Attachment A. 3.3 GROUNDWATER SAMPLING Prior to sampling, each sampling port will be purged until the groundwater is reasonably free of sediment. In addition, temperature, pH, specific conductivity, and turbidity of the purged groundwater will be monitored during purging. Purging will continue until these parameters have stabilized to within a 10 percent variation between measurements. Stabilization of these parameters will be used as an indicator that groundwater entering the sampling port is representative of formation water in the aquifer adjacent to the borehole. Once purging has been completed, groundwater samples will be collected from each sampling port and submitted for laboratory analyses for pesticides (EDB, DBCP, and Sulfolane), California Title 22 Metals, general minerals/characteristics, and total organic carbon. Groundwater samples will be collected directly into laboratory-supplied sample containers using the downhole pumps. One set of duplicate samples will be collected for each analytical parameter to ensure that representative data are obtained and to assess sample reproducibility and evaluate Quality Assurance/Quality Control (QA/QC) of the data. Each sample container will be properly labeled, sealed, and placed on ice in an industrial cooler with proper chain-of-custody documentation for transportation to a California State Certified laboratory. A summary of proposed analyses and analytical methodologies for groundwater sampling is provided in Table 3. 3.4 FIELD DOCUMENTATION Field data sheets will be completed at the time of sample collection and will include the following, as appropriate: • Sampling Date and Time; • Sample Description; • Unique Sample identification Code; • Number and size of sample taken; • Description of sampling point; • Field sample identification number(s); and • Field measurements (pH, temperature, conductivity, etc.). 3 The Source Group,Inc.